Billionaire Warren Buffett's Berkshire Hathaway sold more Bank of America shares, reducing its stake in the U.S. bank by about 14.5 percent since it began a series of share sales in mid-July.

Berkshire sold about 21.1 million shares of Bank of America over the course of Wednesday, Thursday and Friday, worth about $848 million, at an average price of $40.24 per share, according to a new filing on Friday.

Berkshire did not disclose the reasons for reducing its stake in the bank. The company has raised a total of $6.2 billion from selling Bank of America shares since mid-July, adding to a record pile of cash held by Berkshire, which as of June 30 stood at $277 billion.

Berkshire remains the largest shareholder in Bank of America, with 11.4 percent of the shares, worth about $36 billion.

Bank of America is Berkshire's third-largest holding, accounting for about 11 percent of its portfolio, according to CNBC.

Buffett, who turned 94 on Friday, began his investment in Bank of America with a $5 billion deal in 2011, buying preferred stock and options, according to Bloomberg.

Last week, the Omaha elder's company became the first U.S. company outside the tech sector to surpass $1 trillion in market value, joining a club of trillion-dollar companies that includes a handful of companies such as Apple, Alphabet, Meta Platforms and Nvidia.